How the Hybrid Sports Bicycle Works

The prototypes unveiled at auto shows are often the stuff of fantasy -- almost like high-gloss spaceships with tires leaning more toward art than form of transport. In most cases, there's no real intention to manufacture. But who cares? Look at those curves. (The car, too.)

A few of those prototypes, however, are intended for actual street use. One such vehicle, called the Hybrid Sports Bike, or HSB, received a rather warm reception at the 2012 L.A. Auto Show -- not bad for a first-of-its-kind hybrid bike created by a then-grad student over the course of a year [source: Bubilek].

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To be fair, plenty of other vehicles have what the HSB has, but not all-in-one -- a big difference, as we know from the likes of universal remotes, smartphones and Internet-connected, DVD-playing, Blu-ray-equipped video-gaming systems.

The Hybrid Sports Bike is a three-in-one, and the bike's inventor, Tomas Bubilek, drew on some proven approaches to alternative transport that have been around for many years. Those approaches on their own, or even in groups of two, have slipped into the technological mundane, being more than six months old. But they were once pretty exciting in their own right. And, at least for one specific feature, maybe a tiny bit illegal, too.

The Hybrid Bikes We Know

The bike maintains a low center of gravity: Its gas tank is the only heavy component mounted high up.

Hybrid bicycles are old news. As we know them, they combine two forms of power: human-generated, in the form of pedaling, and a second, non-human energy-generator, either electric or gas.

Gas-hybrid bicycles came first, and were simply traditional bikes modified with an add-on kit [source: NYCeW]. Cyclists have long been able to buy wee internal-combustion engines to soup-up their two-wheelers, essentially creating gas-powered motorcycles with working pedals. Not the safest way to travel, perhaps, but a noteworthy upgrade. The engine can be turned off and on to accommodate different power needs, and the whole setup is illegal throughout much of the United States [source: NYCeW]. The modified gas-bike is a difficult vehicle to classify when it comes to traffic laws.

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The more modern, more common, more expensive and quite legal hybrid bicycle is the human-electric variety. These have been around for years and were once a significant development in green transport, particularly in places like the U.S. where nearly half of all car rides stay within a 2-mile (3.2-kilometer) radius of home [source: USDOT]. These types of bikes come in two basic forms: There's the kind with an electric motor than senses the need for extra power automatically, turning itself on when, say, the rider starts up a hill and then shutting off for the ride down; and the kind with an electric motor the rider manually turns on and off as needed.

The Hybrid Sports Bike, or at least the most recent prototype as of March 2013, uses a manual type of electric-hybrid system. What makes the HSB such an interesting machine is that it adds gasoline to the hybrid equation. Dirty, expensive, non-renewable gas.

And yet, the HSB could end up being a significant leap forward in eco-friendlier travel -- in part because the pedals are somewhat ancillary. The HSB is less a hybrid bicycle than a hybrid motorcycle, according to Bubilek, intended for trips well beyond a few miles from home.

There are other hybrid motorcycle designs, most prototypes as well, using two forms of power, either human and electric or gas and electric [source: Ury]. It's the mere option of using solely human power (along with some design choices affecting maneuverability) that helps distinguish the HSB from what's already out there.

The HSB: Taking it Further

The gas engine is mounted low by the pedals, helping center the bike's weight distribution.

The internal combustion engine is not typically considered a "clean energy" add-on. And on its own, that's a fair assessment. What it has going for it, though, when compared to the electric motor, is power. Lots of power.

The Hybrid Sports Bike is a departure from past hybrids in that it uses three sources of energy instead of two: human, electric and gas. The addition of a fossil fuel doesn't make the bike any greener; what it does is make the sometimes gas-sipping bike a more viable alternative to a constantly gas-guzzling car. It has more power and speed, plus a longer range than a bike running with solely electric assist.

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The idea is this: Like the human-electric hybrid bike, the HSB can easily replace a car for quick trips around town. Even the least fit among us can manage a bike ride to the grocery store when an electric motor takes care of the inclines. Unlike the human-electric hybrid, though, the HSB could potentially replace the car for longer trips, and on busier roads, than current hybrid bikes can safely manage.

The "tri-hybrid" HSB, while billed by some as an upgrade on the hybrid bicycle, is really more of a hybrid motorcycle. While human propulsion is part of the power equation, it's not a central one, Bubilek says. Still, the machine looks a lot like a bicycle, albeit a futuristic one, with its 3-inch-wide (7.62-centimeter-wide) wheels and bicycle-style seat, pedals, gears and handlebars. And the bicycle systems all work: For trips to the neighborhood grocery store, there's no need to start up a motor.

For longer trips and higher speeds, though, there are two motors to choose from, electric and gas. Each is activated and deactivated manually via motorcycle-type handlebar controls. As of March 2013, the electric power on the HSB is a 1000-watt motor mounted in the rear wheel hub [source: Bubilek]. The electric battery that charges it is in the hub of the front wheel.

The gas engine is a 110-cubic-centimenter four-stroke, mounted near the pedals. It's on the underside of the frame, helping to keep the center of gravity low.

The gas tank is the only notably heavy component mounted high up, between the handlebars and the seat.

The design, then, focuses a lot on weight distribution. With most of the heavy parts mounted at or below the midline, the bike's low center of gravity allows for a high-speed hybrid motorcycle that can be slimmer and lighter than a traditional one. Bubilek quotes the total weight at 150 pounds (70 kilograms), compared to about 500 pounds (225 kilograms) for a typical sports bike, and the top speed at 70 mph (112 kph) [source: Sport Rider]. That's comparable to the average all-gas-powered scooter and a lot faster than the average, range-limited all-electric one [source: Top Speed].

Who knows about the legality of the tri-powered bike? Talk about difficult to classify. But the prototype represents an innovative approach to eco-friendlier transport that may cause ripples, and traffic regulations will likely have to make adjustments as the hybrid movement unfolds, anyway.

As of early 2013, the inventor is waiting to see if his Hybrid Sports Bike receives as warm a reception from investors as it did from the folks at the auto show. "The next generation of the HSB," Bubilek says, "is geared toward production."

Author's Note: How the Hybrid Sports Bicycle Works

I don't always get to talk to the inventor when I'm writing about something brand new, and I was lucky I did in this case. While I considered it beyond the scope of this article, Tomas Bubilek sent me some documents reflecting his design process, from the first iteration of the HSB to the most recent one. It's pretty cool to see the evolution, especially in sketches, and the steps a particular designer takes in his creative process. Bubilek's Web site is still under construction, but if you're interested, you may want to periodically check it out. He'll hopefully post the start-to-finish sketches sometime soon.